1. Technical Field
The present invention relates generally to cellular wireless networks; and more particularly to the servicing of high data rate packetized data communications within such cellular wireless networks.
2. Related Art
Wireless networks are well known. Cellular wireless networks support wireless communication services in many populated areas of the world. While cellular wireless networks were initially constructed to service circuit-switched voice communications, they are now called upon to support packet-switched data communications as well.
The transmission of packetized data communications within a wireless network places different demands on networks than does the transmission of voice communications. Voice communications require a sustained bandwidth with minimum signal-to-noise ratio (SNR) and continuity requirements. Data communications, on the other hand, typically are latency tolerant but have higher total throughput requirements. Conventional circuit-switched wireless networks were designed to support the well-known voice communication requirements. Thus, wireless networks (as well as conventional circuit switched telephone networks) have been adapted to service data communications, with such adaptation providing mixed results. Thus, future wired and wireless networks will likely be fully packet switched.
Because packet data transmissions typically employ a greater bandwidth on the forward link than they do on the reverse link, various standards have been promulgated which focus on high data rate forward link transmissions. These standards include, for example, the high data rate downlink packet access (HSDPA) standard. The HSDPA is a backward compatible standard that is compatible with the UMTS standard, which is widely used in Europe. The 1xEV-DO and 1xEV-DV standards will also provide high data rate forward link transmissions. These standards will be backward compatible with the 1xRTT standard, which is a member of cdma2000 family of standards. Note that the HSDPA and 1xEV-DO standards typically employ a semi-distributed network architecture.
However, while these high packet data systems provide or high data rate forward link transmissions, they lack the ability to support non-interrupted high data rate transmissions, such as streaming operations. This shortcoming is caused by various problems, including the methodology for selecting cells to service the forward link transmissions as well as the manner in which data is managed within the wireless network.
Thus, there exists a need in the art for a system and method of operation that will support high data rate forward link transmissions capable of supporting non-interrupted transmissions.
In order to overcome the above cited shortcomings of the prior systems, among other shortcomings, a method for operating a cellular wireless network to service high data rate forward link transmissions for a mobile station actively manages the active set of base stations serving high data rate forward link transmissions. As a first operation according to the present invention, interaction with legacy standard operations supported by the cellular wireless network to determine a legacy standard active set of base stations for the mobile station.
Then, a high data rate forward link active set of base stations is determined based upon the legacy standard active set of base stations. Next, the method includes transmitting blocks of packetized forward link data to the base stations of the high data rate forward link active set of base stations. With the packetized forward link data at the base stations, high data rate forward link data is transmitted from only one base station of the high data rate forward link active set of base stations to the mobile station.
According to one aspect of the present invention, the high data rate forward link active set of base stations is a subset of the legacy standard active set of base stations for the mobile station. In one embodiment, the legacy standard operations are code division multiple access operations and the high data rate forward link operates substantially according to a high data rate standard, e.g., the 1xRTT standard and the 1xEV-DO standard, respectively. In such case, the high data rate forward link active set of base stations may correspond directly to a reduced active set of base stations according to the legacy standard operations, e.g., reduced active set.
According to another aspect of the present invention, access to newly added base stations to the high data rate forward link active set of base stations is precluded until the newly added base station is available to support forward link transmissions. According to this aspect, packetized data intended for the mobile station is received at a base station controller. An active set of base stations for servicing the mobile station is determined, wherein any of the active set of base stations may be selected to transmit the packetized data to the mobile station. Initially, transmissions of the packetized data to the mobile station are serviced by a first base station of the plurality of base stations of the active set of base stations.
When a new base station is added to the active set of base stations, however, access must be limited until the base station is ready. Thus, the mobile station""s access to the new base station is delayed to allow provisioning of resources at the new base station. According to one technique, the resources at the new base station are first provisioned, then the mobile station is notified that the new base station is in the active set of base stations. According to another technique, the mobile station is directed to initiate a delay timer for a delay timer period such that it will not attempt to access the new base station until the delay timer has expired. Then, after notifying the mobile station to initiate the delay timer, resources at the new base station are provisioned.
A base station controller and/or other cellular network elements that service high data rate forward link transmissions for a mobile station may perform these operations. Further, these operations may be embodied as a plurality of software operations performed by at least one component of cellular wireless network.
By defining the high data rate forward link active set of base stations via interaction with the legacy standard operations, significant operational resources are conserved. Further, by delaying access to a newly added base station until the base station is ready to provide forward link transmissions, high data rate real-time communications may be supported, e.g., streaming audio, streaming video, etc.
Other features and advantages of the present invention will become apparent from the following detailed description of the invention made with reference to the accompanying drawings.